Process of treating sulfurous arsenic ores.



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ELIAS PETERSSON, OF BRUSSELS, BELGIUM, ASSIGNOR TO THE INTRAOT- ABLE ORETREATMENT COMPANY, LIMITED, OF LONDON, ENGLAND.

PROCESS OF TREATlNG SULFUROUS ARSENIC ORES.

SPECIFICATION forming part of Letters Patent No. 670,140, dated March19, 1901.

Application filed December 30, 1898.

T0 60% whom it may concern.-

Be it known that I, ELIAS PETERSSON,eI1glneer,a Swedish subject,residingat No. 32 Avenue de la Oouronne, Brussels, Belgium, have invented acertain new and useful Process for the Treatment of Sulfurous OresContaining Arsenic,Antimony, and Tellurium, (for which I have appliedfor patents in Italy, dated June 11, 1898, No. 98/35; in Great Britain,dated October 7, 1898; in Sweden, dated December 9, 1898; in Norway,dated December 10, 1898; in Spain,dated December10,l898; in Belgium,dated December 10, 1898,and in France, dated December 10, 1898,) ofwhich the following is a specification.

This invention consists in a process of treatment of sulfurous orescontaining arsenic, antimony, and tellurium whether for extracting thesemetals therefrom or for rendering the said ores capable of treatment byordinary processes with the object of extracting gold, silver, copper,zinc, nickel, lead, &c.

In order to avoid the considerable loss of precious metals accompanyingthe direct roasting of so-called refractory ores for expelling therefromthe arsenic, antimony, and tellurium, various processes have beenproposed with the object of separating the different sulfurets. Theseprocesses are based upon the addition of sulfurets or polysulfurets orof a mixture of alkaline sulfate and carbon,forming the sulfuret duringthe course of the process.

In the process constituting this invention the different sulfurets areset free without any change in their chemical constitution taking place.For this purpose the ore in a finelypulverized state is mixed withcarbon, also reduced to powder, and the mixture is heated in a retort ormuffle-furnace to a temperature which may vary from a dull-red to abrightred heat, according to the nature of the ore. The arsenic is setfree in the state of arsenic- -sulfid vapor and passes away from theretort through a suitable outlet, while the antimony and the telluriumremain in the matter under treatment in the state of sulfurets. Thecarbon prevents all contact of air by destroying the small quantity ofoxygen that may enter the muffle of the furnace and forming carbonicacid; but no chemical action ap- Serial No. 700,759. (No specimens.)

pears to take place, as the carbon remains unchanged. The product whichleaves the furnace after the operation is finished retains itspulverulent condition, not having become agglomerated, as the carbonadmixed with it prevents liquationthat is, it keeps any particles whichmay be melted from running together, the bulk of the carbon remainingunchanged, as above stated. The resulting product may be directlyroasted, then sub jected to washing with acids for the purpose ofremoving therefrom the antimony and telluri um, and subsequently treatedby ordinary processes for extraction of the metals which itcontainsviz.,gold, silver, copper,zinc, &c. As the ore after roastinginthe muffle-furnace still contains most of its sulfur, it may be used inthe manufacture of sulfuric acid.

By way of example I will cite two applica tions which have been made ofthe above process.

First. A finely-crushed pyrite containingfifteen per cent. of arsenichas been mixed with ten per cent. of carbon in powder and the mixturehas been treated for about one hour in a muffle-furnace at a temperatureof about 800 centigrade. All the arsenic sulfid (trisulfuret of arsenic)has become volatilized and'the product obtained contained only traces ofarsenic. By the ordinary processes of roasting and cyanurationninetyeight per cent. of the gold contained in the ore was subsequentlyextracted.

Second. Afinely-crushed antimonialpyrite has been mixed with ten percent. of carbon in powder. The mixture has been heated for about half anhour at a temperature of 700 to 800 centigrade in a muffle-furnace, themass withdrawn from the furnace has been freed from its antimony bycalcination and lixiviation with water acidulated with chlorhydric acid,and the product has yielded the whole amount of gold contained in theore.

It is evident that the carbon which I employ might be replaced by otherorganic matter capable of yielding carbon by calcination. The carbon Iemploy is preferablyin the form of coal.

An ore composed of iron pyrites, mispickel, quartz and gold, silver, andplatinum (or other precious metals) is a typical example of an ore whichcan advantageously be treated by my process. In this ore arsenic existsin combination with iron and sulfur,and the gold is frequently sointimately associated with the arsenic-bearing mineral as to beimpossible of separation by any of the ordinarilyknown means,

When roasted in a finely-divided state admixed with carbonaceousmaterial, also finely divided in a retort or muffle, the arsenic iswholly volatilized as sulfid, the iron pyrites (FeS2) furnishing some ofits sulfur for the purpose and remaining as FeS in the residue, whilethe gold and other precious metals remain untouched and can now beextracted from the non-volatile residuum after an oxidizing calcinationby the employment of ordinary methods, such as amalgamation, cyaniding,due. If antimony be present, the residuum after the second or oxidizingcalcination is subjected to hydrochloric-acid Wash to remove this metalas a soluble chlorid. The arsenic is condensed in the form of sulfids ofarsenic.

Having fully described my invention, What I claim, and desire to secureby Letters Pat ore, in mixing the same with carbon likewise pulverizedand in heating the mixture in a retort or muflie to which all inlet ofair or other gas is precluded and in continuing the heating until thearsenic in the mixture has been driven off from the ore as sulfidWithout material reduction and expelled from the retort substantially asdescribed.

2. A process of treatment of sulinrous ores containing arsenic, andantimony as snlfids in addition to other metals consisting inpulverizing the ore, in mixing the same with carbon likewise pulverized,in heating the mixture in a retort or muifle to which all inlet of airor other gas is precluded and in continuing'the heating until thearsenic has been driven off as sulfid without material reduction andexpelled from the retort, and in afterward calcining the residue left inthe retort and in washing the calcined residue with acid to extract fromit such antimony and tellurium as may be contained in it beforeproceeding to extract the other metals.

In witness whereof I have hereunto set my hand, in presence of twowitnesses, this 16th day of December, 1898.

ELIAS PE'lERSSON.

Witnesses:

H. T.- E. KIRKPATRICK, I. S. KIRKPATRIOIL.

